Vladimir Putin and Barack Obama look set for a frosty meeting later today at the G8 summit, where disagreement over the Syrian civil war has stolen focus from the rest of the agenda.
The Russian president finds himself isolated over whether to aid the anti-Assad rebels, against whom the balance of the two-year conflict has recently turned. And at their first face-to-face meeting in a year, Obama will try to convince him to bring President Bashar al-Assad to the negotiating table.
Last night during an awkward joint press conference with David Cameron, President Putin said the rebels had "blood on their hands."
“One does not need to support people who not only kill their enemies, but open up their bodies, eat their intestines in front of the public and cameras. Are these the people you want to support?" he said.
“Is it them you want to supply with weapons? Then this probably has little relation to humanitarian values that have been preached in Europe for hundreds of years.”
Mr Putin was referring to video footage on the internet of one rebel fighter eating what appeared to be the heart of a government soldier.
Russia has also said it would not allow no-fly zones to be imposed over Syria.
"I think we fundamentally would not allow this scenario," Foreign Ministry spokesman Alexander Lukashevich said in Moscow.
Speaking at the Lough Erne golf resort in Northern Ireland, where the leaders of some of the world's richest countries have convened, Canadian Prime Minister Stephen Harper said of Putin: "We are not, unless there is a big shift in position on his part, going to get a common position with him at the G8."
Mr Cameron, who chairs the G8 summit and has called for intervention on the side of the rebels, acknowledged there was "a big difference" between the positions of Russia and the West on Syria, but stressed there was also common ground.
Syria's civil war, now in its third year, has killed more than 90,000 according to the UN and displaced more than one million. It is fought between forces loyal to President Assad and rebels, mostly from the disparate Free Syrian Army.
The United States said last week it would step up military aid to Syrian rebels - a move which officials said would involve supplying the Western-backed Supreme Military Council with automatic weapons, light mortars and rocket-propelled grenades.
The European Union has also dropped its arms embargo on the country, allowing France and Britain to arm the rebels, though the two countries say they have no immediate plans to do so.
The leaders of the United States, Japan, Canada, Russia, Germany, France, Britain and Italy - representing just over half of the $71.7 trillion (£45 trillion) global economy - also hope to discuss the global economy and trade at the summit.